As many people on this forum will say, an airlock is a poor way to measure if fermentation has stopped. The only way to see, is if you take a hydrometer reading. That being said, even after FG has been met, the yeast still are at work. They are cleaning up after themselves and making your beer taste better. You should probably leave your beer in the primary for 3 weeks before bottling it, just to make sure that it is at its best.
On Tap: Heavenly Scourge Black IPA and Beecave Heffe
Next: Thunderstruck Pumpkin Ale and Pliny the Elder Clone